A recursive discrete-time filter for calculating the impedances from digitized voltage and current samples at relay location is derived. From an interpolating signal model comprising a delaying DC component and components of fundamental harmonic frequencies, an interpolating spectral observer is constructed to give the desired Fourier coefficients recursively. The interpolators are also useful for sampling rates other than Nyquist rate and unevenly spaced samples. The proposed algorithm is tested using fault data recorded at the Saskatchewan Power Corporation, resulting in fast and reliable tripping conditions. The performance of the spectral observer is enhanced by suitable placement of poles of the observer, producing a fast operation of the digital relay. The performance of the protection scheme with evenly spaced data samples is presented

Description:

Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.